CVE Intelligence
CISA KEV Medium Memory corruption

CVE-2018-13383 — Fortinet FortiOS and FortiProxy Out-of-bounds Write

A heap buffer overflow in Fortinet FortiOS 6.0.0 through 6.0.4, 5.6.0 through 5.6.10, 5.4.0 through 5.4.12, 5.2.14 and earlier and FortiProxy 2.0.0, 1.2.8 and earlier in the SSL VPN web portal may cause the SSL VPN web service termination for logged in users due to a failure to properly handle javascript href data when proxying webpages.

Published May 29, 2019 · Updated Oct 13, 2026 · Sources: CISA Known Exploited Vulnerabilities, NIST National Vulnerability Database, GitHub Security Advisories, CVE Program (cve.org) e CISA ADP · CNA: fortinet

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

CISA KEV · Jan 10, 2022 R used by ransomware (CISA)
How the score was calculated
  • Confirmed exploitation (CISA KEV)+35
  • Used in ransomware campaigns (CISA)+10
  • EPSS 33.6% (30-day exploitation probability)+15
  • Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Confirmed
CISA KEV, listed Jan 10, 2022
EPSS FIRST
33.65%
ahead of 98% of scored CVEs · Oct 14, 2026
Affects
Fortinet
Fortinet FortiOS and FortiProxy and 2 more
CVSS base
6.5
Medium · 4 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
Active
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented mitigation — fortiguard.com (NIST National Vulnerability Database)

CISA required action CISA

Apply updates per vendor instructions.

US federal deadline: Jul 10, 2022 — passed 1558 day(s) ago

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Fortinet Fortinet FortiOS and FortiProxy, Fortinet Fortios, Fortinet Fortiproxy).
  2. Treat as emergency remediation: the CVE is in CISA KEV (confirmed exploitation).
  3. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  4. Apply the documented mitigations until a definitive fix is available.
  5. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  6. EPSS ahead of 98% of scored CVEs: prioritize it in the patch queue.
  7. Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Fortinet Fortinet FortiOS and FortiProxy version FortiOS 6.0.0 through 6.0.4, 5.6.0 through 5.6.10, 5.4.0 through 5.4.12, 5.2.14 Vulnerable CVE Program (cve.org) e CISA ADP
Fortinet Fortios ≥ 5.2.0 and < 5.2.15≥ 5.4.0 and < 5.4.13≥ 5.6.0 and < 5.6.11≥ 6.0.0 and < 6.0.5 Vulnerable NIST National Vulnerability Database
Fortinet Fortiproxy < 1.2.9version 2.0.0 Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
6.5 CVSS 3.1 Medium 2.8 3.6 nvd@nist.gov via NIST National Vulnerability Database
6.5 CVSS 3.1 Medium — — GitHub, Inc. via GitHub Security Advisories
4.3 CVSS 3.1 Medium 2.8 1.4 psirt@fortinet.com via NIST National Vulnerability Database
4.3 CVSS 3.1 Medium — — fortinet via CVE Program (cve.org) e CISA ADP
4.3 CVSS 2.0 Medium 8.6 2.9 nvd@nist.gov via NIST National Vulnerability Database
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H (score shown at the top: nvd@nist.gov)
Scoring entities (NIST, CNA, ADP) score independently; each score is shown with its origin. For prioritization we use 6.5 (NVD (NIST)) as a conservative provisional reference — not a definitive official score.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-787 · Out-of-bounds Write

Other CVEs with this weakness →

CISA KEV details CISA

CISA lists a CVE once it has evidence of exploitation against real targets.

Listed
Jan 10, 2022
Federal deadline
Jul 10, 2022
passed 1558 day(s) ago
Ransomware use
Known

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a reference date.

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 33.65%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
  • Hunt retroactively in logs from before Jan 10, 2022 (KEV listing): exploitation may have started earlier.
web/proxy/WAF logsnetwork IDS/IPSendpoint telemetry (EDR)crash dumps

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · fortinet/fortinet fortios and fortiproxy
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Fix documented
    Oct 13, 2026 · NIST National Vulnerability Database
  • Affected products added · fortinet/fortiproxy, fortinet/fortios
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 6.5
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Analyzed
    Oct 13, 2026 · NIST National Vulnerability Database
  • Added to CISA KEV (detected)
    Oct 13, 2026 · CISA Known Exploited Vulnerabilities
  • Record created in this database
    Oct 13, 2026 · CISA Known Exploited Vulnerabilities
  • 2022
  • Added to CISA KEV catalog
    Jan 9, 2022 · CISA
  • 2019
  • CVE published
    May 29, 2019 · fortinet

Source activity

Repeated readings are counted rather than listed.

  • 2× References added · Oct 13, 2026 – Oct 13, 2026
  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

8 on the record

Elsewhere on this site

Fortinet
every CVE for this vendor
2022-01
what else CISA listed that month
Memory corruption
same class
CWE-787
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-106175 A Double Free vulnerability [CWE-415] vulnerability in Fortinet FortiOS 7.6.0 through 7.6.7,... 2d
  • CVE-2026-84392 A NULL Pointer Dereference vulnerability [CWE-476] vulnerability in Fortinet FortiOS 7.4 all... Sep 8, 2026
  • CVE-2026-84393 A improper validation of certificate with host mismatch vulnerability in Fortinet FortiOS 7.6.1... Sep 8, 2026
  • CVE-2026-71407 Stack-based Buffer Overflow in Fortinet Fortios Aug 12, 2026
  • CVE-2026-71408 A allocation of resources without limits or throttling vulnerability in Fortinet FortiOS 7.6.0... Aug 12, 2026
  • CVE-2026-70466 A incomplete list of disallowed inputs vulnerability in Fortinet FortiWeb 8.0.0 through… Aug 12, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2018-13383 is "Fortinet FortiOS and FortiProxy Out-of-bounds Write", rated Medium. It affects Fortinet FortiOS and FortiProxy (Fortinet); versions are in the scope table. It is in CISA KEV: there is evidence of real-world exploitation. CVSS 6.5 describes technical severity. EPSS 33.65% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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